Yes: Take your Phantom to an area that is not near the San Diego airport.
(It's seriously important that you adhere to this to avoid undue attention to yourself and the hobby. It's really there for a reason, even if it may seem annoying.)

(In the event that you didn't want to turn off the feature and just the notification, I don't believe you can at the moment. It's still a new-ish addition to the software. Perhaps after it's been around for a bit, they'll add an option to not show the warning, but still continue to limit the flight ceiling)